Macrolides are a well-known family of antimicrobial agents. Erythromycin A, a 14-membered macrolide, was isolated in 1952 from Streptomyces erythraeus. Examples of macrolides being used as therapeutic agents are roxithromycin, clarithromycin and azithromycin (azalide). Ketolides are semisynthetic 14-membered ring macrolide derivatives, characterized by the presence of a keto function at position 3 instead of L-cladinose moiety present in the macrolactone ring. Telithromycin and Cethromycin are examples of ketolides.
U.S. Pat. No. 4,331,803 discloses the 6-O-methyl derivative of erythromycin i.e. clarithromycin. The U.S. Pat. No. 4,349,545 discloses roxithromycin. The azalide azithromycin is disclosed in U.S. Pat. No. 4,517,359. Telithromycin is described in EP 680967 A1 and corresponding U.S. Pat. No. 5,635,485 and Bioorg. Med. Chem. Lett. 1999, 9(21), 3075-3080. Another ketolide Cethromycin (ABT 773) is disclosed in WO 98/09978, and J. Med. Chem. 2000, 43, 1045.
The U.S. Pat. No. 6,900,183 describes 11,12-γ-lactone ketolides having C-21 of the lactone substituted with cyano or amino derivatives. The patent applications such as U.S. 2004/0077557 and PCT publications WO 02/16380, WO 03/42228, WO 03/072588 and WO 04/16634 disclose 11,12-γ-lactone ketolides. Our co-pending PCT publication No. WO 08/023,248 discloses several Macrolides and Ketolides.